1. Field of the Invention
The invention relates to a device with which flexural or elastic materials can be worked in achieving a desired non-stressed shape, such as a flat shape. Such materials may be substrates or other rollable materials having a constant thickness which are worked as individual sheets or as an endless material web.
2. Description of the Background
Due to it being supplied as a reeled material, for instance, paper tends to curl, i.e. a portion of the web spread out flat is subject to an inherent bending stress and thus tends to curve or curl to relieve the stresses on release of external forces. However, it may also be wanted to bend or work a flat layer which is planar when free of stress so that it assumes a curved position. In any case, bending breaks a predetermined stress by moving the material on its face to which it is to be curved relative to a bending face. In this arrangement the material defines an angle of wrap in the portion coming into contact with the bending face. This angle of wrap is determined by the position of a deflector or guide for the material next the bending face. This deflector may be provided upstream and/or downstream of the bending face. For modifying the angle of wrap or for optionally working both faces of the material the deflector arrangement and the bending face means are expediently adjustable relative to each other. For this purpose the bending face may be positioned on the device frame so that it can be adjusted relative to the deflector during the entire bending operation, e.g. to transpose material sections in sequence having continuously changing tendencies into the same, non-stressed planar shape or the like. Such an adjustment may, however, result in a bulky configuration involving complicated control and inertia in control movements which makes it difficult to quickly react to varying curl tendencies or other properties of the material. If the length of the material section tensioned freely or linearly between the bending face and the deflection face is greater than the deflection radius of the deflection face the aforementioned drawbacks are likewise given and in addition to this material section may oscillate at high running speeds to the detriment of consistent good quality working.